Plumbing the Planet: The 5 Biggest Projects Taking on the World's Water Supply

As nations and regions all over the globe face too much polluted water and too little fresh water, they are turning to some of the largest, most technologically complex projects the world has ever seen. Here, we have compiled five of the biggest and most ambitious. But are they big enough to keep the taps flowing?

The dire statistics are well-known, but deserve repeating: One in six people in the world live without regular access to clean water, according to the United Nations, and one in three lacks access to decent sanitation. Even countries with good water supplies—like the U.S.—will experience trouble sustaining them in the near future, as panelists discussed at the water roundtable PM hosted last fall.

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The United States has its share of ambitious water infrastructure—that's how cities such as Los Angeles exploded from the desert—but it doesn't solve the problem of vanishing supplies. The snowpack in the California mountains is down to 61 percent of a normal year, authorities there say. U.S. Secretary of Energy Steven Chu recently expressed his concerns for the long-term consequences. "I don't think the American public has gripped in its gut what could happen," Chu told the Los Angeles Times on Wednesday. "We're looking at a scenario where there's no more agriculture in California. I don't actually see how they can keep their cities going," either.

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At the same time, urban areas like New York and Tokyo are grappling with the problem of too much water all at once. A projected consequence of global warming, besides drought, is the accelerated cycle of what used to be 100-year storms. Around the world, countries are trying to combat these problems with ever-more-clever engineering: bigger and badder treatment plants, pipelines, tunnels and reservoirs. Here are five projects hoping to be big and bad enough.

Ashkelon Desalination Plant, Israel

An Israeli employee inspects membranes that extract salt from the water at Ashkelon's seawater reverse osmosis (SWRO) plant, south of Tel Aviv. Ashkelon's desalination plant is one the biggest in the world. (Photograph by David Buimovitch/AFP/Getty Images)

Two thousand years ago, sailors took boilers aboard their ships in order to distill seawater into fresh water for drinking. Today the largest desalination plants in the world, in Saudi Arabia and the United Arab Emirates, rely on the same principle to create hundreds of thousands of cubic meters of fresh water apiece. But distillation requires a great deal of energy (think about the gas required to heat water for tea, then imagine trying to boil enough water to sate an arid nation). New desalination plants use a less energy-intensive method—reverse osmosis. Rather than heating water to its boiling point, reverse osmosis forces water through membranes that capture the salts.

The Ashkelon Desalination Plant, which opened in 2005, converts more than 26 billion gallons of Mediterranean Sea water into fresh water for the State of Israel each year—5 to 6 percent of total demand. Ashkelon is not only the largest reverse-osmosis desalination plant in the world, it's also one of the few public plants to recover waste heat to improve efficiency and reduce costs. The process does require heat, though not as much as distillation. Reverse osmosis works best when the water is around 95 to 100 F. And while the Ashkelon plant operates at the low end of the desalination cost spectrum (52 cents per cubic meter of water) it's still not cheap, at more than $51 million a year.

North-South Water Transfer Project, China

Long before an industrial explosion put China's natural resources under intense strain, the country suffered a water problem. The mountainous southern region takes in ample precipitation, while the northern region, which has swelled to include more than 200 million people, must rely on limited groundwater supplies. In the 1950s, Communist leader Mao Zedong proposed moving water around the country to balance the scales. Now, half a century later, China has broken ground on the plan, called North-South Water Transfer Project. When construction finally ends in 2050, the system will feature three different lines: a 716-mile diversion called the "Eastern Route," a 786-mile "Central Route," and 310-mile "Western Route."

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Moving water across long distances is incredibly energy-intensive—and yet valuable energy is also lost along the way. Even if the pipes are designed to take advantage of gravity, they require dampers every few meters to slow the force of the rushing water. China isn't the only country to consider huge water transfer projects—a handful are proposed for the western U.S.—but this nationwide, decades-long engineering project takes the cake as the world's most ambitious. "That takes the insanity to a whole new level," says Mark Shannon of the University of Illinois and director of the Center for Advanced Materials for the Purification of Water with Systems. While it's a remarkable feat, he points out that extended drought, reduced snow packs and melting glaciers are affecting water supplies world over, including China's. Even a massive transfer project might not guarantee a constant flow of water.

G-Cans Tunnel System, Tokyo, Japan

On street level, Tokyo is the world's most populated metropolitan area, with more than 30 million people crammed into the city. But far below the teeming mass of humanity lies a sprawling system of cavernous tunnels, which are empty most of the time. These tunnels make up G-Cans, a system in the Saitama area, on the outskirts of Tokyo, designed to protect the Japanese capital from flooding in the summer wet season. While much of the world is grappling with potable fresh water shortages caused by chemical pollution and drought, global warming could also exacerbate the severe storms that flood many highly populated areas.

If the waters around Tokyo rise to dangerous levels, G-Cans' 14,000-hp turbines will begin pumping water out of the Edogawa River and into one of five containment silos—each of which measures about 105 ft in diameter and 213 ft deep. The tunnels connecting those silos stretch about 4 miles, making G-Cans the world's largest underground waterway. If you find yourself in Tokyo, you can tour this colossal underground complex for free—just bring a Japanese translator.

Marina Reservoir, Singapore

Even before much of the world became aware of the pending water shortage, Singapore was in a tough spot when it came to collecting fresh water. This tiny country consists solely of urban area surrounded mostly by sea, so residents, who now count nearly 5 million strong, had few places from which to draw drinking water. As the population grew, the threat of a water shortage heightened. With limited options, the government blocked off one of the city's harbors to create an artificial reservoir.

The Marina Barrage, which opened in November, is a dam that spans the 1,150-ft Marina Channel. The nine crest gates, each more than 90 ft high, act as a barrier to keep seawater out of the Marina Reservoir. If it rains during low tide, the barrier is lowered to release water; during high tide, pumps inside the dam can blast water out. Meanwhile, fresh water from precipitation continues to pour in. After one or two years of this cycling, it should be a purely freshwater reservoir.

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Singapore's government says that the Marina Reservoir's catchment—the area from which it collects water—amounts to one-sixth of the nation's land area. So while Singapore might not have much land, it's collecting fresh water from as big an area as possible.

Groundwater Replenishment System, Orange County, Calif.

The Groundwater Replenishment System in Fountain Valley, CA is a $480 million dollar water treatment system, the largest of its kind in the world, that converts the sewage water of Orange County into drinking water. (Photograph by Mary Knox Merrill/The Christian Science Monitor/Getty Images)

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In some respects, Orange County got lucky: It is one of the few places in California with an ample supply of groundwater, according to Shivaji Deshmukh of the Orange County Water District. But a growing population increased demand for water, and heavy consumption brought with it an even more serious problem: When the groundwater level started to sink below that of the sea, saltwater from the Pacific Ocean came dangerously close to leaching in and ruining the county's supplies.

To fight back against this seawater intrusion, California scientists built a barrier—one made of water, not of concrete. First, engineers use reverse osmosis, micro-filtration and UV radiation to purify wastewater, which would normally be discharged into the ocean, to drinking water standards. Then, using a 3-mile stretch of 36 wells, about 5 miles from the coast, they inject the reclaimed water in the ground. The wells, Deshmukh says, resemble pipes with perforations. The pressurized water forms a dam between the ocean and the groundwater basin, keeping saltwater at bay.

Orange County first tried this method in 1975, but the new Groundwater Replenishment System, which began operation in January 2008, can create and inject almost 15 times more purified water, Deshmukh says. This allows the county to expand the seawater barrier and keep up with population growth. With current rates of freshwater withdrawal, he told PM, it takes about 30 million gallons every day to maintain the barrier.